1. Field of the invention
The present invention relates to a fuel injection valve for injecting fuel.
2. Description of the Related Art
Atomization of fuel injected from a fuel injection valve is important to ensure that exhaust discharged from an engine conforms to emission regulations, and to improve fuel efficiency. To improve the atomization of fuel, the diameter of an injection hole, through which fuel having passed through a valve seat flows, can be small. In making the diameter of the injection hole small, it is preferable to shorten the length of the injection hole, in order to achieve the desired injection characteristics by reducing the pressure loss in the injection hole. Thus, when the injection holes are formed in an injection hole member, it is necessary to thin the thickness of a plate of the injection member. Thinning the plate of the injection hole member, however, makes it difficult to secure adequate strength of the injection hole member. Accordingly, the injection hole member is attached to a nozzle body with, for example, a separate holding member (refer to Japanese Patent Laid-Open Publication No. 2000-73918, hereinafter called as “patent document 1”). Otherwise, the injection hole member has a thin portion where the injection holes are to be formed, and a thick portion for securing its adequate strength (refer to Japanese Patent Laid-Open Publication No. 11-117832, hereinafter called as “patent document 2”). Thus, the strength of the injection hole member, and the strength of a connection section between the injection hole member and the nozzle body are secured.
When the injection hole member is held by the holding member, as disclosed in patent document 1, a step is formed between an end face of the injection hole member on the opposite side to the nozzle body, at which outlets of the injection holes are open, and an end face of the holding member on the opposite side to the nozzle body. Also in the technique disclosed in patent document 2, a step is formed between the thick portion and the thin portion of the injection hole member, at which outlets of the injection holes are open. A quantity of fuel injected from the injection holes adheres to the periphery of the injection holes. Thus, when the step is formed in the vicinity of the injection holes, the fuel adhering in the vicinity of the injection holes accumulates in the vicinity of the step by surface tension, without dispersing in the air. If the fuel accumulated in the step is solidified by ambient heat, the injection holes may be clogged. As a result, there is a possibility that the desired injection characteristics will not be achieved.